135 gas timing info

I have been having problems with my fathers massey 135 that has the perkins 3 cylinder gas engine. The dealership tried to get it running properly but within a week it is back to the way it was. Out of frustration I left it. I picked it up today from the farm and brought it to my garage where my tools are and I have heat to work.

I am going to start from scratch starting with ignition (carb has been rebuilt by dealer and checked over by a friend that rebuilds carbs on the side so I have ruled out carb issue for now) I am wondering where the timing marks are on the perkins gas engine. There is a hole in bell housing on left side of engine but have also read there is marks on the pullys. Need to know this as this spot will be where I point the timing light. I believe the continental and perkins have different timing mark locations and that's why I cant seem to get a definitive answer.
Any help is appreciated.

If I recall Perkins is on the front pulley. Think at idle it should be ten degrees BTDC, but will check my books later. High idle timing advance is about 25 if I recall. May be wrong but it will get you close for now.

Wouldn't suspect timing this quick after it was running, sounds like fuel problems such as trash or rust in the tank or a flooding issue. Pull a plug to see if its wet and if dry give it a shot of carb cleaner in the cylinder then see if it tries to start.

Can you expand more on not running properly? Does it at least start or will it not start at all any longer? If it does start is it spitting or popping or what exactly is it doing?

The tractor would start but would backfire and to keep it running I would have to constantly manipulate the choke. I did not suspect carb as the dealer rebuilt it and I also had a friend who rebuilds zenith and marvel as a hobby look at it aswell. I tried to start it yesterday while I was loading it and it flooded and would not fire. I went out today and tried to start it and it started pouring fuel out of carb and flooded. Some googling has shown this is quite normal when choking too much. I drained the fuel and will be putting new in. I did have good fuel flow while draining it with and without fuel filter so fuel supply starvation I believe is ruled out.

I cleaned the plugs and have good spark. I also turned engine over to #1 tdc and found my timing marks at the bellhousing on flywheel. Static timing looks close I will be putting timing light on it soon to perkins spec of 12deg btdc. I am also going to drop fuel bowl and check for sediment in bottom.

Basically enough time has passed that I am going to start at beginning and eliminate as I go. I will post back once I am to the point of running again. Thanks for help this far.

Having to manipulate the choke like that is a pretty good sign of fuel issues. If you have nice blue spark and manually aligning the timing is "pretty close", it should start and run ok. What happens when you try to rev up the engine? Does it spit, sputter and die or... ?
Which carb do you have? Zenith or Marvel?

Sometimes a lite tap on the carb will dislodge whats stuck under the needle jet causing the flooding issue. Take out the plugs and let them dry then replace and cut off gas till it fires off then try cutting the gas on to run. Looks like a inline fuel filter may help or either another carb rebuild. Is the main jet turned out 1 an 1/4 from all the way in?